1. Field of the Invention
The present invention relates to digital devices. More specifically, the present invention relates to a copy management system and method for controlling the reproduction and recording of digital content on and from at least one digital device.
2. General Background
Analog communication systems are rapidly giving way to their digital counterparts. Digital television is currently scheduled to be available nationally to all consumers by the year 2002 and completely in place by the year 2006. High-definition television (HDTV) broadcasts have already begun in most major cities on a limited basis. Similarly, the explosive growth of the Internet and the World Wide Web have resulted in a correlative growth in the increase of downloadable audio-visual files, such as MP3-formatted audio files, as well as other content.
Simultaneously with, and in part due to, this rapid move to digital communications system, there have been significant advances in digital recording devices. Digital versatile disk (DVD) recorders, digital VHS video cassette recorders (D-VHS VCR), CD-ROM recorders (e.g., CD-R and CD-RW), MP3 recording devices, and hard disk-based recording units are but merely representative of the digital recording devices that are capable of producing high quality recordings and copies thereof, without the generational degradation (i.e., increased degradation between successive copies) known in the analog counterparts. The combination of movement towards digital communication systems and digital recording devices poses a concern to content providers such as the motion picture and music industries, who desire to prevent the unauthorized and uncontrolled copying of copyrighted, or otherwise protected, material.
In response, there is a movement to require service providers, such as terrestrial broadcast, cable and direct broadcast satellite (DBS) companies, and companies having Internet sites which provide downloadable content, to introduce protection schemes. Two such copy protection systems have been proposed by the 5C group of the Data Hiding Sub Group (DHSG) (5C comprising representatives of Sony, Hitachi, Toshiba, Matsushita, and Intel) and the Data Transmission Discussion Group (DTDG), which are industry committee sub-groups of the Copy Protection Technical Working Group (CPTWG). The CPTWG represents the content providers, computer and consumer electronic product manufacturers.
The DTDG Digital Transmission Copy Protection (DTCP) proposal is targeted for protecting copy-protected digital content, which is transferred between digital devices connected via a digital transmission medium such as an IEEE 1394 serial bus. Device-based, the proposal uses symmetric key cryptographic techniques to encode components of a compliant device. This allows for the authentication of any digital device prior to the transmission of the digital content in order to determine whether the device is compliant. The digital content is itself encoded prior to transmission so that unauthorized copying of the content will result in copy having an unintelligible format.
One method of encoding the content has been proposed by the DHSG, and is based on watermarking techniques. Although the main focus of the DHSG proposal has been for copy protection of digital movie and video content, particularly as applied to DVD systems, it is expected to be applicable to the copy protection of any digital content distributed electronically via digital broadcasts and networks. The watermarking techniques, which are invisible to the user, allow the incoming content to be marked in a manner that makes it extremely difficult to discern precisely how the content was encoded, and thus extremely difficult to remove or alter the watermark without damaging the content. The DHSG has determined three primary cases of detection and control that such a technology should accomplish: playback, record and generational copy control. It is anticipated that the watermarking technology will allow the content provider to specify at least whether the content is “copy never,” “copy once,” and “copy free” content. “Copy never” is used to mark digital content to indicate that the content is not allowed to be copied, while “copy free” indicates that the content may be copied freely and which can be marked with additional information. This is different than material that is never marked. Finally, “copy once” is used to indicate that the digital content is allowed to be copied only once. As a copy is being made, the original “copy once” content and the newly copied content are re-marked with “no more copy.” Of course, other types of copy management commands may limit the playing or reproduction of such digital content; for example, to a specific period of time, duration, or number of plays or viewings.
Thus, even today, the functionality of digital devices such as set-top boxes, digital televisions, digital audio players, and similar such digital devices extends beyond their historical role of conditional access (CA), i.e., merely descrambling content to a CA-clear format for real-time viewing and/or listening, and now include constraints and conditions on the recording and playback of such digital content. For example, currently, copying of scrambled content for subsequent descrambling and viewing or listening may be permitted with the appropriate service/content provider authorization or key provided to the digital device.
A disadvantage of such digital devices is that do not allow the simultaneous viewing of content in a CA descrambled format (hereinafter referred to as “descrambled content”) and the recording of content in a CA-scrambled content (hereinafter referred to as “scrambled content”), both of which are typically copy-protected, using, for example, using some sort of watermarking process, as proposed by the DHSG. Thus, the digital devices support either the viewing of descrambled content or the recording of such scrambled content, but not both. Additionally, in those instances where the digital device is connected to other digital devices over a transmission medium via a digital interface, there may also be additional encoding at the digital interface prior to input into the transmission medium; e.g., using the 5C-proposed copy-protection scheme. In such cases, the viewable form, e.g., descrambled content, with “copy never” attributes would not be recordable by downstream devices. However, the non-viewable, or scrambled, content would typically have “copy free” attributes. As the simultaneous viewing of descrambled content and the recording of scrambled content is not possible under these scenarios, it is difficult to “time shift” copy-protected content and impossible to record a scrambled program while it is being viewed, even though such recording is for the viewer's/listener's sole entertainment at a later point in time. Both are considered desirable by viewers, listeners and other consumers.
Therefore, in view of the interests of the aforementioned viewers, listeners and other consumers, it would be desirable to provide a system that allows for the simultaneous viewing, listening or playing of descrambled content and recording of the scrambled content which also addressed the concerns of the various content providers.